The purpose of this project is to gain knowledge about the molecular mechanisms of normal and aberrant brain development. In order to experimentally approach this problem, we study the development of the murine cerebellum. Underlying developmental processes are changing patterns of gene expression. By cloning those genes whose expression changes during cerebellar development we identify genes potentially involved in particular aspects of cerebellar development. In order to find an indication of the genes' function we will analyze the phenotypes of mice homozygous for a mutated version of these genes. Understanding the processes involved in normal brain development will give us important keys in understanding the relationship between development and mental performance as well as aberrant development and mental illness.